Australian swimmer Chloe McCardel jumps feet-first from Marina Hemingway in Havana, on June 12. McCardel is attempting to become the first to cross the Florida Straits swimming through the shark-infested sea without a protective cage.

By Petra Cahill, NBC News

Updated on June 6 at 10:30am ET: After swimming for 11 hours, McCardel abandoned her attempt due to a "severe debilitating jelly fish sting," according to a statement from her support team.

Australian endurance swimmer Chloe McCardel jumped feet-first into the water off of Cuba Wednesday in an attempt to become the first person to swim from Havana to Florida without a protective shark cage.

Arriving at Havana’s Hemingway Marina in a pink 1950s Chevy convertible, McCardel thanked her Cuban hosts, promising she’d be back again. Her husband helped lather grease around the edges of her one-piece bathing suit to prevent chafing as she put on her swim cap and goggles.

Desmond Boylan / Reuters

Australian long-distance swimmer Chloe McCardel starts her attempt to swim to Florida from Havana June 12. With favorable weather predicted and a team of scientists on her side, McCardel will set out on Wednesday to become the first person to make the 103-mile (166-km) swim between Cuba and the Florida Keys without a shark cage to protect her. The treacherous body of water known as the Florida Straits is the Holy Grail for marathon swimmers and has been conquered only once, by Susie Maroney, also Australian, who used a protective cage at age 22 during her 1997 swim that glided on ocean currents and enabled her to make the journey in just 25 hours.

The approximately 100 mile swim through shark and jellyfish infested waters from Havana to the Florida Keys is expected to take about 60 hours.

Roberto Leon / NBC News

Australian endurance athlete Chloe McCardel strokes through the balmy waters off Cuba in an attempt to become the first person to swim from Havana to Florida without a protective shark cage. She is accompanied by kayakers and a support boat.

McCardel is not the first to attempt the crossing without a cage; two other swimmers have made four failed attempts since 2011.

“More than 20 people across history have tried to swim across this amazing stretch of water, the entire Gulf Stream, with the sharks, the jelly fish over such a long distance, 103 miles, about 166 kilometers and it is the hardest swim in the world today,” McCardel said during a press conference in Havana Tuesday.

She laid out the perimeters of the challenge: “I will not wear a wet suit. I will not use a shark cage. I will not hold on to anything. I will not get on the boat at any time.”

Adalberto Roque / AFP - Getty Images

Australian swimmer Chloe McCardel gives her thumbs up before departing from Marina Hemingway in Havana, on June 12. McCardel will attempt to become the first to cross the Florida Straits swimming through the shark-infested sea without a protective cage.

McCardel has an extensive team of scientists who will be helping her navigate the finicky Gulf Stream from land – feeding information to her support boat. She will also be deploying a piece of equipment called a Shark Shield to create an electromagnetic field around her meant to discourage the predators from getting too close, according to the Associated Press.

With a graceful freestyle stroke she set out accompanied by two kayakers and her support boat.

NBC News' Roberto Leon and the Associated Press contributed to this report.